Proteolytic processing of the Aplysia egg-laying hormone prohormone

Proteolytic processing of the Aplysia egg-laying hormone prohormone

Department of Chemistry and Beckman Institute, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801

Edited by Wendell Roelofs, Cornell University, Geneva, NY, and approved December 30, 1997 (received for review November 3, 1997)

Abstract

By using matrix-assisted laser desorption/ionization time-of-flight MS, individual peptidergic neurons from Aplysia are assayed. A semiquantitative method is developed for comparing single-cell profiles by using spectral normalization, and peptides are localized to specific cells by mass spectrometric cell mapping. In addition to all previously identified products of the egg-laying hormone (ELH) gene, other peptides are formed from proteolytic hydrolysis of Leu-Leu residues within ELH and acidic peptide (AP). AP exhibits further processing to yield AP_1–20 and AP_9–27. These peptides appear to be colocalized in vesicles with ELH, transported to specific neuronal targets, and released in a Ca²⁺-dependent manner. A differential peptide distribution is observed at a specific target cell, and a low-frequency variation of AP, [Thr²¹]AP, is detected in a single animal.

Footnotes

↵ * To whom reprint requests should be addressed at: University of Illinois at Urbana-Champaign, Department of Chemistry, 600 S. Mathews Avenue, Box 63-5, Urbana, IL 61801. e-mail: sweedler{at}bozo.scs.uiuc.edu.
This paper was submitted directly (Track II) to the Proceedings Office.
Abbreviations: AP, acidic peptide; ASW, artificial seawater; BCP, bag cell peptide; DHB, 2,5-dihydroxybenzoic acid; ELH, egg-laying hormone; MALDI, matrix-assisted laser desorption/ionization; pELH, egg-laying hormone prohormone; TOF MS, time-of-flight MS; NPY, neuropeptide Y.
A commentary on this article begins on page 3338.